| 三峡库区望霞危岩体孕灾地质环境条件分析 |
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| 引用本文：乐琪浪,王洪德,高幼龙,薛星桥,王高峰,孙向东.2015.三峡库区望霞危岩体孕灾地质环境条件分析[J].地球学报,36(2):204-212. |
| DOI：10.3975/cagsb.2015.02.09 |
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| 基金项目:中国地质调查局地质调查项目(编号: 12120113008200) |
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| 中文摘要:危岩体是一种典型的灾害地质体, 其形成、变形与破坏受控于地质环境条件, 地质基础要素在孕灾的过程中起着决定性作用, 各基本地质要素与灾害形成的关系是研究危岩体变形规律和破坏机理的关键性问题。通过对三峡库区望霞危岩体区域地质构造作用分析, 横石溪背斜构造解析, 各类地质结构面发育特征统计和危岩体岩性组合方式及工程地质条件剖析, 结合危岩体两次变形破坏过程, 分析各因素对危岩体的形成及变形的关系。研究认为: 孕育望霞危岩体的横石溪背斜雏形形成于印支期的隆升阶段, 至燕山主期形成褶皱主体, 后期则以继承性改造为主, 危岩体的形成及孕育主要集中在背斜核部区域, 枢纽位置尤为发育。控制危岩体变形的5条关键裂缝与顶部发育的“V”字形裂缝关系密切, 其是在纵弯褶皱作用下背斜顶部脆性岩层受到强烈的拉裂影响, 叠加台阶式层间滑动作用, 形成与轴面近于平行的拉张裂缝。在望霞危岩体中发育多组地质结构面, 其中原生结构面对各条关键裂缝及关键块体提供基础背景值, 控制其规模、范围及变形强度。控制着变形关键部位特别是前缘软弱层变形位置、牵引区段及强烈程度。构造结构面主要控制关键裂缝的延伸方向、距离及样式, 控制关键块体的变形方向, 裂解范围及规模, 掉块及崩裂位置, 控制危岩体底部关键部位即压张裂缝的形成位置、张开度及位移方向。次生结构面主要控制后缘变形区, 对各条关键裂缝控制其继承性变形, 控制关键块体扩张, 对岩体裂解破坏至关重要。同时, 望霞危岩体在地层岩性上构成了典型的硬—软—硬岩性组合, 为危岩体的变形提供了地质结构组合条件, 其底部大面积的采空区控制着危岩体整体滑塌变形。 |
| 中文关键词:三峡库区 危岩体 地质条件 岩体结构 层间滑动 |
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| An Analysis of Disaster-pregnant Geological Environment Conditions of the Wangxia Unstable Rock Mass in the Three Gorges Reservoir |
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| Abstract:Unstable rock mass is a typical kind of hazard geological body. Its formation, deformation and damage are controlled by the geological environmental conditions. Geological basic elements play a decisive role in the disaster-pregnant process. The relationship between geological basic elements and the formation of the disaster is the key issue in the study of the deformation regularity and failure mechanism of the unstable rock mass. The authors made an analysis of such relationship on the basis of the regional geological tectonism, the Hengshixi anticline structure, the development of geological structural planes, the lithologic combination and the engineering geological conditions, in conjuction with the unstable rock mass deformation and failure process. The researches show that the Hengshixi anticline structure that bred the Wangxia unstable rock mass was formed at the uplift stage in Indo-Chinese epoch. The fold appearance was formed mainly in Yanshanian, and later gave way to inheritance transformation. The unstable rock mass was formed mainly in the arch core area, particularly the hinge position of the fold. The five kinds of critical cracks that controlled the deformation of the rock mass had close relationship with the "V"-shaped cracks at the top of the rock. The brittle rock at the top of the anticline was affected by strong tensile splitting under the influence of buckle fold effect and the superposition of the stepladder interlayer-gliding effect. As a result, the tensile cracks almost parallel to the axial surface of fold were formed. Groups of geological structural planes were developed in the Wangxia unstable rock mass. The primary structural plane provides background for every critical crack and block, controls the scale, range and strength of the deformation, and also governs the deformation critical parts, especially the location, traction sections and intensity of the frontal weak layer. The tectonical plane mainly controls the extension direction, distance and style of the critical cracks, as well as the deformation direction, the cracking range and scale, the fall-block and split position of the critical blocks; it also governs the unstable rock mass at the bottom of the critical parts in such aspects as the location of pressure tension crack, the opening degree and the displacement direction. The secondary plane mainly controls the deformation at the back edge area, the inheritance deformation of the critical cracks and the expansion of the critical block, thus playing an important role in the formation of cracking damage of the unstable rock mass. In addition, the stratigraphic lithology of the Wangxia unstable rock mass constitutes a typical hard-soft-hard lithologic combination, and provides geological structural combination condition for the deformation of the rock. The large mined-out area at the bottom controls the overall slump deformation of the unstable rock mass. |
| keywords:Three Gorges Reservoir unstable rock mass geological conditions structural plane characteristics interlayer-gliding |
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